This product looks very sturdy and attaches firmly to your glasses. The length is not adjustable. It will not keep your glasses from sliding down your nose. I had to tie a figure-8 knot in the retaining wire (to shorten it) to make it hold my glasses so that they would slip down my nose while bicycle riding. The retaining wire is thin, but looks strong, and does not absorb water or sweat. The cord may be too short if you like to hang your sun glasses around your neck while indoors.